Monoclonal antibodies to hormone and factor receptors of human cells will be produced. These will be used in various combinations to kill cancer cells in culture and to inhibit tumor growth in nude mice. Screening methods will be developed to search for hybridomas that produce high quantitites of high affinity antibodies to receptors. Screening and selection methods will be developed for searching for mutants which produce high levels of growth factors. Combinations of protein chemistry and recombinant DNA techniques will be used to characterize novel growth factors. (CS)